cc1plus is a component of a C++ compiler. You're trying to compile a C program. The gcc command determines which compiler to invoke based on the name of the source file: a C compiler for .c, a C++ compiler for .cc or .C, a Pascal compiler for .p, an assembler for .s, etc.

It seems that you gave your program a name that indicates a C++ program. Do note that Linux file names are case sensitive. C source files must have the extension .c (lowercase c), not .C. Unix users tend to use mostly lowercase letters in file names, and in particular almost all conventional file extensions are in lowercase. So make sure to use lowercase file names.